PDCD1 and lung cancer: Modern immunotherapy takes advantage of the inhibition of particular immune checkpoint molecules present on immune cells (cytotoxic T-lymphocyte antigen 4, CTLA-4, programmed cell death 1 protein, PD-1) or tumor cells (PD-L1) with specific monoclonal antibodies and currently is used for treatment not only of advanced melanoma, but also lung cancer, renal cancer, and others [1].